The grim story of how Larry Nassar sexually abused hundreds of girls under the cover of his role as USA Gymnastics team doctor and Michigan State University physician before finally being convicted touches on so many issues — sports, education, medicine, justice, misogyny — that no single feature documentary could possibly capture its maddening scope.

And yet Erin Lee Carr’s “At the Heart of Gold: Inside the USA Gymnastics Scandal” is a compellingly woven true-crime primer that serves both the gist of what happened while exploding your consciousness over what needs to be done in the future.

Told mainly through interviews with victims, loved ones, observers and journalists — interspersed with archival footage of Nassar with gymnasts that will chill your blood considering what we know now — Carr’s movie is essentially in three parts: the cruel training circumstances that allowed kind-faced Nassar to get away with his assaultive “technique,” the painstaking effort to bring him and others to justice, and his trial. The last third, which makes memorable use of the sentencing portion’s heartbreaking victim impact statements — there were 204 in all — is like a cascade of arias bringing a grand tragic opera to its mournful close.

Hearing from the girls, whether from the courtroom footage or in testimonials for Carr’s camera, is ultimately what makes “At the Heart of Gold,” even in its no-nonsense execution, necessary viewing. What they endured demands our attention.